SOLUTION

The resultant force $F_R$ is shown graphically in Fig. $2-37$b$.$ We can express this force as a Cartesian vector by first formulating $F_{AB}$ and $F_{AC}$ as Cartesian vectors and then adding their components. The directions of $F_{AB}$ and $F_{AC}$ are specified by forming unit vectors $u_{AB}$ and $u_{AC}$ along the cables. These unit vectors are obtained from the associated position vectors $r_{AB}$ and $r_{AC}.$ With reference to Fig. $2-37$a$,$ to go from $A$ to $B,$ we must travel $\{-4k\}m,$ and then $\{4i\}m.$ Thus,